With a dramatic increase in the number of complete bacterial genomes in the public and private databases, there exists an outstanding opportunity for the identification of new antibacterial protein targets. Interestingly, the accumulation of genomic sequences has been punctuated by the realization that typically greater than one third of any genome cannot be annotated for function based on sequence similarity. Several of these "unknowns" have been shown to be genetically validated drug discovery targets. However, without a defined biochemical activity, unknowns that prove to be essential for growth and viability are intractable for the purposes of drug discovery. Biochemical assay of protein function is critical to the implementation of high-throughput screening to discover lead compounds, to the determination of a detailed enzyme mechanism, and to the successful optimization of those leads to tight-binding inhibitors and ultimately to efficacious drugs. The proposed research aims to break new ground in the problem of defining general functional assays, and in understanding the biochemical activities of proteins of unknown function. The experimental basis for our proposed methodology involves microcalorimetry and substrate libraries. In this research proposal, we aim to demonstrate the technology by identifying substrates for enzymes of unknown function from E. coli, determining the enzyme mechanisms of these proteins, and designing inhibitors based on the mechanisms. Establishment of the technology proposed here enables a procedure for the selection of validated enzyme targets and for the identification of novel antibacterial drug candidates to combat drug resistant pathogens. PROPOSED COMMERCIAL APPLICATION: The invention disclosed here provides a method for identifying substrates and inhibitors for new enzyme targets identified through genomic sequencing. As applied to proteins of unknown function from bacterial genomes, the method of substrate profiling allows one to establish assays for anti-bacterial lead compound discovery in the pharmaceutical industry. The annual world wide market for antibiotic compounds is in excess of $23 billion. Single product sales can exceeed $1 billion. The technology described here enables the discovery of novel antibiotics.